[clang] [NFC] Add API documentation and annotations (PR #78635)

[Joshua Batista via cfe-commits]

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@@ -570,7 +716,13 @@ double4 sin(double4);
 //===----------------------------------------------------------------------===//
 // sqrt builtins
 //===----------------------------------------------------------------------===//
+
+/// \fn T sqrt(T Val)
+/// \brief Returns the square root of the input value, \a Val.
+/// \param Val The input value.
+
 #ifdef __HLSL_ENABLE_16_BIT
+_HLSL_AVAILABILITY(shadermodel, 6.2)
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bob80905 wrote:

Surprisingly, it looks like there aren't function prototypes for half2/3/4, and I imagine we would want this new attribute applied to such aliases. Just a note for the future.

https://github.com/llvm/llvm-project/pull/78635